A process for dewatering sludges containing solid matter and water using an amine or amine mixture having an inverse critical solution temperature is described in Emanual, U.S. Pat. No. 3,899,419. An improvement on that process is described in Ames, U.S. Pat. No. 3,925,201, issued Dec. 9, 1975 and assigned to the assignee hereof. A process for breaking sludges containing oil, water and sludges using amines having an inverse critical solution temperature with water is described in Ames & Peters, U.S. Pat. No. 4,002,562.
In Emanual, U.S. Pat. No. 3,899,419 a sludge is mixed with an amine or mixture of amines having an inverse critical solution temperature with water. At a temperature below the inverse critical solution temperature of the amine, the water in the sludge and any oily materials in the sludge will dissolve in the amine. The solid materials in the sludge can then be removed to leave a more or less single-phase mixture. Increasing the temperature of the single-phase mixture above the inverse critical solution temperature of the amine results in the formation of a two phase system: a water component containing residual amine, and an amine component containing residual water. Any oily matter which was in the sludge will remain with the amine component and can be treated with various processes. The water component may be further processed or recycled.
A problem not solved by the Emanual process is loss of the amine in the water component caused by the difficulty of removing the residual amine from the water component. There may also be further loss of the amine in the solid matter separated from the mixture. The loss of amine is problematic, particularly total recycling of amine is desired and where purity of end products is important.
Ames, U.S. Pat. No. 3,925,201 discloses a method for minimizing the residual amine in the solid matter and in the water component which method includes adding an alkaline composition to the sludge before addition of the amine. The alkaline composition is mixed into the feed stock prior to addition of the amine. However, practicing the Ames '201 invention has proven that addition of the alkaline composition to the sludge before addition of amine leads to greatly increased viscosity of the sludge making mixing and pumping of the sludge very difficult.
Expensive, heavy-duty mixing and pumping equipment may be required to achieve mixing and transport of the sludge-alkali mixture. Furthermore, the process taught by Ames U.S. Pat. No. 3,925,201 does not provide a convenient, accurate method for controlling the amount of alkali added to ensure that the amount added is adequate to reduce loss of amine.
Thus, there exists a need in the art for a method of minimizing the residual amine in the solid matter separated from the sludge and in the water component produced by the Emanual U.S. Pat. No. 3,899,419 process and of controlling the amount of alkali added to ensure that the amount added is adequate and to avoid the problems of increased viscosity of the sludge produced by the Ames U.S. Pat. No. 3,925,201 method.